The __ standard provides WLAN bandwidth of up to 54Mbps in the 5GHz frequency spectrum. The 802.11a standard also uses a more efficient encoding system, orthogonal frequency division multiplexing (OFDM), rather than FHSS or DSSS

802.11a

The __ standard provides for bandwidths of up to 11Mbps (with fallback rates of 5.5, 2, and 1Mbps) in the 2.4GHz range. The 802.11b standard uses DSSS for data encoding. The 802.11b and 802.11a standards are incompatible for two reasons: frequency and modulation. 802.11b operates in the 2.4GHz frequency and uses DSSS. 802.11a runs at 5GHz and uses OFDM.

802.11b

The __ standard provides for bandwidths of 54Mbps in the 2.4GHz frequency spectrum using OFDM or DSSS encoding. Because it operates in the same frequency and can use the same modulation as 802.11b, the two standards are compatible. However, you should know that there are some interoperability concerns to be aware of. 802.11b devices are not capable of understanding OFDM transmissions; therefore, they are not able to tell when the 802.11g access point is free or busy. To counteract this problem, when an 802.11b device is associated with an 802.11g access point, the access point reverts back to DSSS modulation to provide backward compatibility. This means that all devices connected to that access point will run at a maximum of 11Mbps. To optimize performance, you should upgrade to all 802.11g devices and set the access point to G-only. One additional concept you need to know about when working with 2.4GHz wireless networking is channels. Although 14 channels have been defined, youre only allowed to configure your wireless networking devices to the first 11. When you install a wireless access point and wireless NICs, they will all auto-configure their channel and this will probably work okay for you. If you are experiencing interference, changing the channel might help. And if you have multiple, overlapping wireless access points, you will need to have non-overlapping channels. The three non-overlapping channels are 1, 6, and 11.

802.11g

The standard claims to provide for bandwidth up to 600Mbps. It works in both the 2.4GHz and 5GHz ranges. __ achieves faster throughput a couple of ways. Some of the enhancements include the use of 40MHz channels, multiple-input multiple-output (MIMO), and channel bonding. Remember how 802.11g uses 22MHz channels? 802.11n combines two channels to (basically) double the throughput. MIMO means using multiple antennas rather than a single antenna to communicate information. (802.11n devices can support up to eight antennas.) Channel bonding allows the device to simultaneously communicate at 2.4GHz and 5GHz and bond the data streams, which increases throughput. One big advantage to __ is that it is backward compatible with 802.11a/b/g. This is because __ is capable of simultaneously servicing 802.11b/g/n clients operating in the 2.4GHz range as well as 802.11a/n clients operating in the 5GHz range.

802.11n

__ accomplishes communication by hopping the transmission over a range of predefined frequencies. The changing, or hopping, is synchronized between both ends and appears to be a single transmission channel to both ends.

Frequency-hopping spread spectrum (FHSS) FHSS

__ accomplishes communication by adding the data that is to be transmitted to a higher-speed transmission. The higher-speed transmission contains redundant information to ensure data accuracy. Each packet can then be reconstructed in the event of a disruption.

Direct-sequence spread spectrum (DSSS) DSSS

__ accomplishes communication by breaking the data into subsignals and transmitting them simultaneously. These transmissions occur on different frequencies or subbands.

Orthogonal frequency division multiplexing (OFDM)

__ to allow communications with a specific access point. The __ is basically the network name. Because by default wireless routers will broadcast their __. If its not secured, they can connect within a few seconds. You can configure the router to not broadcast and then manually set up your clients with the __ of the device.

SSIDs

__ was one of the first security standards for wireless devices. It uses a static key; the client needs to know the right key to gain communication through a __-enabled device. The keys are commonly 10, 26, or 58 hexadecimal characters long. You may see the use of the notation __. x, which refers to the key size; 64-bit and 128-bit are the most widely used, and 256-bit keys are supported by some vendors. __.64 uses a 10-character key. __.128 uses 26 characters, and __.256 uses 58. __ is vulnerable due to the nature of static keys and weaknesses in the encryption algorithms.

Wired Equivalency Protocol (WEP)

__ is an improvement on WEP that was first available in 1999 but did not see widespread acceptance until around 2003. Once it became widely available, the WiFi Alliance recommended that networks no longer use WEP in favor of WPA. This standard was the first to implement some of the features defined in the IEEE 802.11i security specification. Most notably among them was the use of the Temporal Key Integrity Protocol (TKIP) . Whereas WEP used a static 40- or 128-bit key, TKIP uses a 128-bit dynamic per-packet key. It generates a new key for each packet sent. __ also introduced message integrity checking. When __ was introduced to the market, it was intended to be a temporary solution to wireless security. The provisions of 802.11i had already been drafted, and a standard that employed all of the security recommendations was in development. The upgraded standard would eventually be known as WPA2.

WiFi Protected Access (WPA)

__ implements all of the required elements of the 802.11i security standard. Most notably, it uses Counter Mode CBC-MAC Protocol (CCMP), which is a protocol based on the Advanced Encryption Standard (AES) security algorithm. CCMP was created to address the shortcomings of TKIP, so consequently its much stronger than TKIP.

WiFi Protected Access 2 (WPA2)

One of the oldest ways of communicating with ISPs and remote networks is through __ connections. Although its not used much anymore due to limitations on modem speed, which top out at 56Kbps. The biggest advantage to __ is that its cheap and relatively easy to configure. The only hardware you need is a modem and a phone cable.

Dial-Up/POTS

__ utilizes existing phone lines and provides fairly reliable high-speed access. To use __, you need a __ modem and a network card in your computer. You use an Ethernet cable with an RJ-45 connector to plug your network card into the __ modem and the phone cord to plug the DSL modem into the phone outlet. Typically, you will plug the phone cord into a __ splitter and plug the splitter into the wall. The splitter does two things for you. One, it allows you to still plug your phone into the same connection. Two, it filters the noise from the __ modem so you dont hear it when you are on the phone. The most popular in-home form of DSL is ADSL.

Digital Subscriber Line (DSL)

__, supports download speeds that are faster than upload speeds. __ and your voice communications can work at the same time over the phone line because they use different frequencies on the same wire. Regular phone communications use frequencies from 0 to 4kHz, whereas __ uses frequencies in the 25.875kHz to 138kHz range for upstream traffic and in the 138kHz to 1104kHz range for downstream traffic. One major advantage that __ providers tout is that with DSL you do not share bandwidth with other customers, whereas that may not be true with cable modems.

Asymmetric DSL (ADSL)

__ Internet provides broadband Internet access via a specification known as Data Over Cable Service Internet Specification (DOCSIS). While __ generally is faster, a big caveat to these speeds is that they are not guaranteed and they can vary. One of the reasons that speeds may vary is that you are sharing available bandwidth within your distribution network. The size of the network varies, but is usually between 100 and 2,000 customers. Another reason is that __ companies make liberal use of bandwidth throttling.

Cable Internet

__ is a digital, point-to-point network capable of maximum transmission speeds of about 2Mbps, although speeds of 128Kbps are more common. __ uses the same two-pair UTP wiring as POTS. What makes __ different from a regular POTS line is how it uses the copper wiring. Instead of carrying an analog signal, it carries digital signals. A computer connects to an __ line via an __ terminal adapter, referred to as an __ TA.

Integrated Services Digital Network (ISDN)

The data is carried on a channel called a Bearer channel , or __, which can carry 64Kbps of data.

B channel

The second type of channel is used for call setup and link management and is known as the signal channel, or __. This channel has only 16Kbps of bandwidth.

D channel

A typical 144Kbps basic rate interface __line has two B channels and one D channel. One B channel can be used for a voice call while the other is being used for data transmissions, or both can be used for data. When the B channels are combined to maximize data throughput (which is common), the process is called bonding or inverse multiplexing. Multiple __ lines can also be bonded together to form higher throughput channels. __ is also known as 2B+D because of the number and type of channels used. __ is more common in Europe than it is in the United States.

(BRI) ISDN

__, also known as 23B+D, which means it has 23 B channels and one D channel. The total bandwidth of a 23B+D __ line is 1536Kbps (23 B channels n 64Kbps per channel + 64Kbps for the D channel). This is typically carried on a dedicated T1 connection and is fairly popular in the United States.

Primary Rate interface (PRI) ISDN

__ is pretty impressive with the speed and bandwidth it delivers. __ is because it is much more expensive than copper to install and operate. The cables themselves are pricier, and so is the hardware at the end of the cables. Technology follows this inevitable path of getting cheaper the longer it exists, and __ is really starting to embrace its destiny. Some phone and media companies are now offering __ connections for home subscribers. An example of one such option is FiOS, offered by Verizon.

Fiber-Optic Internet

__ service, which means that the cables are 100 percent fiber from their data centers to your home. At the time we were writing this book, the fastest speeds offered were 150Mbps download and 35Mbps upload.

Fiber-to-the-Home (FTTH)

__ runs fiber to the phone or cable companys utility box near the street and then runs copper from there to your house. Maximum speeds for this type of service are around 25Mbps.

Fiber-to-the-Node (FTTN)

Instead of a cabled connection, it uses a __ to receive data from an orbiting satellite and relay station that is connected to the Internet. __ connections are typically a lot slower than wired broadband connections, often maxing out at around 4Mbps. __ is often referred to as line of sight wireless because it does require a clear line of sight between the user and the transmitter. Another drawback to satellite technology is the latency. The latency occurs because of the length of time required to transmit the data and receive a response via the satellite. This delay (between 250 and 350 milliseconds) comes from the time it takes the data to travel the approximately 35,000 kilometers into space and return. __ connections are incredibly useful when you are in an area where its difficult or impossible to run a cable or if your Internet access needs are mobile and cellular data rates just dont cut it. The second advantage is due to the nature of the connection. This type of connection is called point-to-multipoint because one __ can provide a signal to a number of receivers simultaneously.

Satellite

Many cell phone providers offer network cards that allow your laptop computer or other device to connect to the Internet from anywhere you can get a cell signal. Some will bundle that service with your normal monthly cell service at no additional charge, while others will charge you an incremental fee.

Mobile Hotspots MiFi

__ refers to a generation of standards for mobile phones and telecommunication services that fulfill the International Mobile Telecommunications-2000 (IMT-2000) specifications as adopted by the International Telecommunication Union (ITU). In more practical terms, its simply a standard for wireless telephone, Internet, video, and mobile TV. To meet IMT-2000 standards, the service must provide peak data rates of at least 200Kbps. There are two major branches of __ standards worldwide. The first is Universal Mobile Telecommunications System (UMTS), which is used in Europe, Japan, and China. Its basically an outgrowth of the GSM standard. The second is CDMA2000, which is used in the United States and South Korea.

3G

A __ card such as this allows you to connect up to five WiFi-enabled devices (802.11b/g) as a __ cloud to get Internet access. The connection the __ card will make back to the cell phone provider will most likely be EVDO based. After you purchase a __ device, you first connect it to your laptop via USB cable for activation and setup.

MiFi

In concept, think about __ as a fast network run over cell towers. __ was intended to be an alternative to DSL or cable modems as an Internet access method, whereas WiFi is clearly entrenched as a LAN standard. __ has seen its greatest successes so far in MAN-type settings and has a practical range of about 5 miles. There are a few problems with __. First, its not backward compatible with existing 2G and 3G technologies. Second, while its relatively fast (5Mbps to 6Mbps downloads and 2Mbps to 3Mbps uploads), its not as fast as originally promised. Third, it costs a lot and requires a lot of power.

World Wide Interoperability for Microwave Access (WiMAX)

__ looks to be a more promising 4G alternative. Its faster than WiMAX (up to 12Mbps down and 5Mbps up), backward compatible with 3G and WiMAX, and more stable than WiMAX. Many networks today are a hybrid of wired and wireless connections. Understand the fundamentals of how each works separately; then you can understand how they work together. Every wireless connection eventually connects back to a wired network point somehow.

Long Term Evolution (LTE)

__ is a service that translates private IP addresses on your internal network to a public IP address on the Internet. If you are using your wireless router to allow one or more clients to access the Internet but you have only one external public IP address, your router is using __.

Network Address Translation (NAT)

NAT is specifically a one-to-one translation of a private IP address to a public IP address. If you have multiple client computers with private addresses accessing the Internet using one public address (called many-to-one), that is a specific form of NAT known as overloading, or __.

Port Address Translation (PAT).

__ is an easy way for novice users to set up and configure a secure wireless network. With literally the push of a button on the wireless router, client computers would be able to connect to the router using the secure WPA2 encryption method. Its a very similar concept to configuring a remote for your garage door opener.

WiFi Protected Setup (WPS)

By enabling__, you can limit the computers that have access to your network.

MAC filtering

Some firewalls have a third network port for a second semi-internal network. This port is used to connect servers that can be considered both public and private, such as web and email servers. This intermediary network is known as a __.

Demilitarized zone (DMZ)

__ firewall is implemented on a single machine so it protects only that one machine. This type of firewall is usually a software implementation because you dont need any additional hardware in your personal computer to run it. All current Windows client operating systems come with Windows Firewall, which is a great example of a __ solution. __ firewalls are generally not as secure as network firewalls, but for small businesses or home use, theyre an adequate, cheap solution.

Host-based

A __ firewall is what companies use to protect their private network from public networks. The defining characteristic of this type of firewall is that its designed to protect an entire network of computers instead of just one system. Its generally a stand-alone hardware device with specialized software installed on it to protect your network.

Network-based

The default configuration of a firewall is generally__, which means that all traffic is blocked unless specifically authorized by the administrator. While this is very secure, its also time consuming to configure the device to allow legitimate traffic to flow through it.

Default deny

__ means all traffic is allowed through unless the administrator denies it.

default allow

__ is the set of rules that determines which traffic gets through the firewall and which traffic is blocked.__ are typically configured to block traffic by IP address, port number, domain name, or some combination of all three. How you configure your __ is sometimes referred to as port assignment or setting up rules. Packets that meet the criteria in the ACL are passed through the firewall to their destination. This is known as port forwarding.

Access control list (ACL)

__ is essentially an automated form of port forwarding. It allows traffic to enter the network on a specific port after a computer makes an outbound request on that specific port. For example, if a computer on your internal network makes an outbound Telnet request (port 23), sub-sequent inbound traffic destined for the originating computer on port 23 would be allowed through.

Port triggering

__ is a strategy that allows an administrator to control resources to maintain a certain service level. By using __, an administrator can set different priorities for one or more types of network traffic based on different applications, data flows, or users. For example, if the engineering group needs to have a certain amount of guaranteed network bandwidth, __ can make that happen. This is not typically implemented on small or home office networks but rather for larger enterprise networks. __ focuses on dealing with five different types of problems that can affect data on a network: Delay, usually caused by congested routes that prevent critical data from arriving on time Dropped packets, which often causes delay. Error, or corrupted data Jitter, or variation in packet delay in a data stream. Out-of-order delivery, which can cause performance issues in time-sensitive applications such as VoIP. Before each session, a __ level is established as part of a service-level agreement (SLA). This is a simply priority setting. Higher-level numbers indicate higher priority, and administrators can set priority levels 0 through 5. As more and more real-time business-critical applications hit the market, __ will become a bigger topic.